Ladders having collapsible and expandable ladder sections are used in order to make the ladder smaller for storage and transport purposes.
In the European patent EP-B1-0 527 766 a collapsible ladder is described comprising ladder bars divided into sections interconnected by rungs. In each ladder section is provided retaining or locking mechanisms, designed to automatically release the upper ladder sections, when a rung reaches a lower rung. This means, that subsequent to the release of the lowermost ladder section, the following ladder sections are automatically released, whereby the ladder collapses.
In the European patent EP-B1-1 402 143 another collapsible ladder is described comprising a retaining or locking mechanism on each ladder section. The locking mechanism is provided at both sides of a ladder section and is designed to be manually and individually released at both sides of a ladder section to collapse a ladder section. The locking mechanism on every ladder section needs to be released to completely collapse the ladder.
One drawback with the ladder described in EP-B1-0 527 766 is that the locking mechanism is positioned on the second lowermost ladder section, which makes it rather uncomfortable to release the ladder. One drawback with the ladder described in EP-B1-1 402 143 is that every ladder section needs to be released individually by the user, which could be rather tiresome for the user. Yet another and greater drawback is if any of the locking mechanisms of EP-B1-0 527 766 or EP-B1-1 402 143 are used in a step-ladder, since both locking mechanisms enable a stepladder having any of these locking mechanisms to be used even though they are not completely extended or if one side of the stepladder is folded or extended more or less than the other side of the stepladder.
There is a wish to provide a locking mechanism for a collapsible ladder or stepladder that combines the benefits of the described prior art solutions without their drawbacks and that ensures the collapsible ladder or stepladder can only be used when the ladder is completely extended.